I'm 15 years old and I've been working out for about 7 to 8 months. I regularly trained with a PT, with whom I did traditional, high-rep, low-weight, cardio, and machine exercise. Thankfully, I would like to, immediately, start my first, true linear progression scheme (I'm looking at GSLP. Recommendations appreciated, though). Particularly, I've gotten very excited about starting to track my progress, weights, etc. However, I don't quite know where to start.

What are some good ways to record, organize, and graph my physical fitness? I've been tooling with google sheets (excel), and this seems to be what most people are doing. How do you track your lifting progress, and could you perhaps provide a link or picture? Furthermore, do you keep a calendar and schedule? How, and where? Thanks.